This invention relates to a digital camera and an image processing method for preparing composite images such as composite prints obtained by compositing images of two or more subjects.
Digital exposure is a technology by which image information recorded on a film is read photoelectrically and converted to digital image data which are then subjected to various steps of digital image processing before image recording is carried out. This technology has recently been commercialized as the digital photoprinter which generates characters and other image data by image data processing and combines them with the image data of film images, thereby facilitating the production of composites of the film images with the characters, etc.
In the recently developed digital electronic still camera (hereunder referred to simply as the digital camera), an image captured by shooting is recorded as digital image data in a recording medium such as the internal memory built in the digital camera or an IC card and on the basis of the recorded digital image data, the captured image is displayed on a printer or monitor or a composite image is created within the camera. A model is known that can make a single composite by pasting a template to an image taken with the digital camera. Exemplary templates include images such as frames and illustrations and characters such as those in calendars and greeting cards.
If desired, digital image data may be input into the digital photoprinter direct from the recording medium in the digital camera by an image input means so that compositing and various other steps of image processing are performed in the digital photoprinter.
Various methods of image compositing have been known in the art. To mention one approach, an image taken by an image pickup means and additional information as received by a dedicated means from an external device are stored in separate regions and images are presented on a display means as switched between an individual image and a composite. Another approach is for assembling two consecutive images into a panoramic image and involves comparing the overlaps of the two images in lightness and correcting them to have a lightness match.
Unexamined Published Japanese Patent Application (kokai) No. 304227/1198 discloses a digital camera in which the subject being photographed is Presented on the display unit of the camera and overlaid with an already recorded image to facilitate shooting from a fixed position; the disclosed camera has another feature of adding a splice mark to the displayed image so that a big enough panoramic picture can be taken easily. Unexamined Published Japanese Patent Application (kokai) No. 142682/1993 discloses a digital camera which, when caking a panoramic picture, shifts an already recorded image horizontally so that an end of it is displayed within the viewfinder of the camera to facilitate registration for the picture to be taken next.
According to another method, a plurality of photographed images are composited by image processing with personal computers or the digital photoprinter using commercial image processing software such as Adobe's Photoshop®.
However, these prior art methods have had various problems. Consider, first, the case of creating a composite image by pasting a template to a picture taken with the digital camera; usually, the template is preliminarily stored in the camera or recording medium as image data under such conditions as to produce an appropriate output image but the picture is not necessarily an appropriate image and often requires retouching of density, color and gradation due to unsatisfactory exposure conditions, shooting light source and subject's scene. Unless the template is simple enough, it is difficult to distinguish between the template and the picture in the composite and the template image and the pictured image cannot be retouched independently of each other. On the other hand, if one attempts to retouch the whole composite image, the template which has been appropriate is not so any longer. This problem can be dealt with by checking the picture on the liquid-crystal screen of the digital camera, making the necessary adjustments and taking another picture of the scene but this approach is not practically feasible since the photographer either misses the shutter release opportunity or spends an undesirably long time before the final composite is output.
Consider next the case where the picture taken with an image pickup means and the additional information received from an external device are presented on a display means as switched between an individual image or a composite. If a personal computer (PC) is wired as the external device, the picture may be clipped from the composite with a template on the PC screen and subjected to subsequent image processing but this simply requires a lot of manpower. What is more, the image retouched on-screen does not always agree in quality with he image from an output device, indicating the inadequacy of retouching on the display device of the PC which is not calibrated for the output image. The third approach of compositing two consecutive images by matching them in lightness has the problem of limited applicability to the purpose of compositing a photographed image with a preliminarily stored template image.
The digital camera disclosed in Unexamined Published Japanese Patent application (kokai) No. 304227/1998 is primarily intended for achieving registry in taking pictures from a fixed position or shooting a panoramic picture and therefore unsuitable for selecting more than one subject in a scene to create a composite image. The digital camera disclosed in Unexamined Published Japanese Patent Application (kokai) No. 142682/1993 is also unsuitable for assembling two or more subjects since its principal objective is to achieve registry in taking a panoramic picture by simply presenting an end of the photographed image.
The use of commercial image processing software on a personal computer or digital photoprinter tends to produce composite images that do not look natural if individually photographed images of subjects are to be assembled.